It has been known that an injection hole disposed in a nozzle tip portion of an injector injecting a fuel into a cylinder of an internal combustion engine may be subjected to corrosion because acid-containing moisture causes dew condensation in and condensed water adheres to the nozzle tip portion. Whether the dew condensation in the nozzle tip portion occurs or not is affected by the relationship between the temperature of the nozzle tip and the dew point of the in-cylinder atmosphere. In view of this point, PTL 1 proposes corrosion reduction by means of nozzle tip temperature estimation and EGR amount adjustment based on the estimated nozzle tip temperature.